Process and apparatus for heating a cross stream shaft furnace in view of heating solid materials, particularly for the calcination of limestone



9, 1960 H. EIw. HE'ILIGENSTAEDT I 2,948,521 PROCESS AND APPARATUS FOR HEATING A CROSS STREAM SHAFT FURNACE IN VIEW OF HEATING SOLID MATERIALS, PARTICULARLY FOR THE CALCINATION 0F LIMESTONE Filed-July 11, 1957 2,948,521 n I PROCESS AND APPARATUS FOR HEAIING A 'CROSS STREAM SHAFT'FURNACE IN-VIEWOF HEATING SOLID MATERIALS, PARTICULARLY FOR THE CALCINATION OF LIMESTONE is A.

Hans Erich Werner Heilig'eustt'iedt .Volklingen, to l e Eiseu- .und Stahlwerke G.m.b.H., Volklingen, Germany, a firm of Germany FiledJuly 11, 1951, Ser. No.- 671,137: Claims P r y; application Germany July 14,1956

5 Claims; or. 263- 29) i The present invention relates to a crossstreamshaft I furnace for the heating of solid materials, particularly for the calcination of limestone, in which the'materia'l moves downwardly by gravity and in which heating gases are forced transversely through said material. More over, the main feature consists in that the heating gases are mixed with vre-circulated .waste gases which come from the zone of temperature essentially determining the heat consumption required to carry out theoperation.

After controlling the temperature of the heating gases by mixing them with recirculated waste gases from'the roasting zone, the heating gases enter the shaft on one side and leave it on the other side. As a result thereof, the material moving downwardly on-that side of the shaft on which theheating gases leave the shaft, is heated with gas of lower temperature than that on the other side. Consequently, this material is less intensively heated than that moving dovmwardly on the gas inlet side. As the passage time of the material in the furnace depends on the efliciency of the roasting at the most unfavourable point, the output of the furnace is determined by the roasting time at the gas outlet side.

According to the present invention, the passage time can essentially be shortened and, thus, the output of the furnace essentially be increased by heating the shaftfurnace in a closed circuit. For this purpose, the roasting zone of the shaft is divided into two parts of substantially equal height in such a manner that the gas collecting chambers on both sides of the shaft are divided in the middle of their height, forming thus several chambers situated on both sides of the shaft. The recirculated gases traverse these chambers in a closed circuit and are subjected at the same time to an intermediate heating.

The accompanying drawing illustrates a shaft-furnace for the performance of the process according to the present invention.

The calcining zone 1 of the shaft is divided into two parts of substantially equal height, thus forming four chambers 2, 3, 4 and 5. The gas leaving the shaft 1 through numerous ports in the wall between the shaft and the gas collecting chamber 2 enters this chamber 2 from which it is drawn by the injector 6 into the heating chamber 8. The injector 6 is actioned by means of gas supplied to the nozzle 7. In the heating chamber, the gas is heated to the required temperature by means of fuel introduced through the main and burned in the burner 9 after having been mixed with hot air supplied from the cooling zone by the main 11.

From the heating chamber 8, the gas passes through the gas collecting chamber 3, traverses the shaft and enters the opposite gas collecting chamber 4. The injector 6' provides the suction of the gas from the collecting chamber 4 into the heating chamber 8' where the gas is heated in the same manner :as in the heating chamber 8. After heating in this chamber, the gas passes through the gas collecting chamber 5, traverses the shaft in inverse direction and enters the gas collecting chamber 2, where the circuit begins again. By virtue of this closed circuit of the gas, the heating of the material contained in the upper part on the left side-of the shaft as well as that contained in the lower part on the right side of; the shaft, is acceleratedu l ---WhatI'claimis:';-* TI i i l. Amethod ofl calcining, comprising the steps of causing material forcalcining to flow through a pair of consecutively arranged calcining zones; passing hot cal cining gas -in a direction of how substantiallytransversal to the direction offl'owof sa'id' material through one of said calciningzones, so as to heat "that material flowing through said" one calcining zone by heat exchange with said hot calcining gas,-said -calcining gas being'cooled during said heat exchange; reheating the thus cooled gas emanating fromsaidone calcining zone; passing the thus reheated calcining gas through the other of said calcining zones in a-direction substantiallytransversal "to the flow of said material and substantially opposite'to the direction of flow of said 'gas' through said one calcining zone,

so as 'to heat material flowing through the other of said calcining zones by heat exchange with said reheated calcining gas, the same being cooled during said heat exchange; reheating the thus cooled gas emanating from said other calcining zone; and recycling said reheated gas by introducing the same into said one calcining 'zone, thereby substantially evenly heating the entire material during the flow thereof through said: pair of calcining zones. v

2. A method of calcining, comprising the steps of causing material for calcining to fiow downwardly through a pair'of consecutively -arran'ged substantially vertically extending calcining zones;'pass'ing hot calcining gas in substantially horizontal direction of flow substantially tranversal to the direction of flow of said material through one of said calcining zones, so as to heat that material flowing through said one calcining zone by heat exchange with said hot calcining gas, said calcining gas being cooled during said heat exchange; reheating the thus cooled gas emanuating from said one calcining zone; passing the thus reheated calcining gas through the other of said calcining zones in a substantially horizontal direction substantially transversal to the flow of said material and substantially opposite to the direction of flow of said gas through said one calcining zone, so as to heat material flowing through the other of said calcining zones by heat exchange with said reheated calcining gas, the same being cooled during said heat exchange; reheating the thus cooled gas emanating from said other calcining zone; and recycling said reheated gas by introducing the same into said one calcining zone, thereby substantial-1y evenly heating the entire material during the flow thereof through said pair of calcining zones.

3. A calcining apparatus, comprising in combination, a kiln or vertical shaft type including a vertical shaft having consecutively arranged therein an upper and a lower heating zone said vertical shaft including an inlet portion located above said upper heating zone, and an outlet portion located below said lower heating zone, so that material introduced into said inlet portion will move downwardly through said upper and lower heating zones to said outlet portion; first means for passing hot gas in a substantially horizontal direction of flow through one of said heating zones that first means having an inlet and an outlet end; first heating means connected to the outlet end of said first means for receiving gas passed through that one heating zone and for heating the same, said first heating means having an outlet end; second means for passing the thus heated gas through the other of said heating zones in a substantially horizontal direction substantially opposite to the direction of flow of said gas through that one heating zone, that second means having an inlet and an outlet end and said inlet end of said second means being connected to said outlet end of said first heating means; second heating means connected to the outlet end of said second means for receiving gas passed through that other heating zone and for reheating the same, said-second heating means being connected to the inlet end of said firstmeans for delivering reheated gas thereto.

4. A calcining apparatus, comprising in combination, a kiln of vertical shaft type including-a vertical shaft having consecutively arranged therein an upper and a lower heating zonesaid vertical including an inlet portion located above said upperheating zone, and an outlet portion located below saidlower heating zone,

so that material to be calcined when introduced into said inlet portion will move downwardly through said upper and lower heatingzones to said outlet portion; first means for passing hot gas in a substantially horizontal direction of flow through the upper of said heating zones that first means having an inlet and an outlet end; first heating means connected to the outletend of said first means for receiving gas passed through that one heating zone and for heating the same, said first heating means having an outlet end; second means for passing the thus heated gas through the lower of said heating zones in a substantially horizontal direction substantially opposite to the direction of flow of said gas through that one heating zone, that second means having an inlet and an outlet end and said inlet end of said second means being connected to said outlet end of said first heating means; second heating means connected'to the outlet end of said second means for receiving gas passed through that other heating zone and for reheating the same, said second heating means being connected to the inlet end of said first means for delivering reheated gas thereto.

5. A calcining apparatus for calcining solid material, comprising in combination, a kiln of vertical shaft type including a vertical shaft having consecutively arranged therein an upper and a lower heating zone of substantially equal length adapted for downward gravitational flow therethrough of said material said vertical shaft including an inlet portion located-above said upper heating zone -and anoutlet portion located below said lower heating zone, ;so that material introduced into said inlet portionwil-l move. downwardly through said upper and lower heating zone to said outlet portion; first means for passing hot gas in a substantially horizontal direction of flowt'ransver'sef to they direction of flow of said downward-flowing material through the upper of said heating zones that first means having an inlet end and an injector forming outlet end; first. heating means including a burner connected to the injector forming outlet end of said first meansfo'r receiving gas passed through that one heating zone and for heating the same said first heating means having an outlet end; second means for passing the thus heated gas through the lower of. said heating zones in a substantially horizontal direction substantially opposite to the direction of flow of said gas through that one heating zone, that second means having an inlet end and an injector forming outlet end and said inlet end of said second means being connected to said outlet end of said References Cited in the file of this patent UNITED STATES PATENTS 1,562,764 Harris Nov. 24, 1925 2,667,342 Ellerbeck Ian. 26, 1954 2,687,879

Heiligenstaedt Aug. 31,1954 

3. A CALCINING APPARATUS, COMPRISING IN COMBINATION A KILN OR VERTICAL SHAFT TYPE INCLUDING A VERTICAL SHAFT HAVING CONSECUTIVELY ARRANGED THERIN AN UPPER AND A LOWER HEATING ZONE SAID VERTICAL SHAFT INCLUDING AN INLET PORTION LOCATED ABOVE SAID UPPER HEATING ZONE, AND AN OUTLET PORTION LOCATED BELOW SAID LOWER HEATING ZONE, SO THAT MATERIAL INTRODUCED INTO SAID INLET PORTION WILL MOVE DOWNWARDLY THROUGH SAID UPPER AND LOWER HEATING ZONES TO SAID PORTION, FIRST MEANS FOR PASSING HOT GAS IN A SUBSTANTIALLY HORIZONTAL DIRECTION ON FLOW THROUGH ONE OF SAID HEATING ZONES THAT FIRST MEANS HAVING AN INLET AND AN OUTLETS END, FIRST HEATING MEANS CONNECTED TO 